Inductive heated injector using additional coil

ABSTRACT

A fuel injector assembly includes a first coil that induces a time varying magnetic field into a second coil that is utilized to heat fuel flowing through the fuel injector. The second coil generates a second magnetic field generated by a current induced by the first coil into the second coil. The induced current is generated by an alternating current signal that is interposed onto a direct current signal sent to the first coil. The second coil also is electrically connected to pass current induced from the first coil into a component in thermal contact with the flowing fuel. The current from the secondary coil resistibly heats the component to provide an alternate mode of heating fuel flow.

CROSS REFERENCE TO RELATED APPLICATION

The application claims priority to U.S. Provisional Application No.60/786,335 which was filed on Mar. 27, 2006.

BACKGROUND OF THE INVENTION

This invention generally relates to a fuel injector for a combustionengine. More particularly, this invention relates to a fuel injectorthat heats fuel to aid the combustion process.

Combustion engine suppliers continually strive to improve emission andcombustion performance. One method of improving both emission andcombustion performance includes heating or vaporizing fuel beforeinjection into the combustion chamber. Heating the fuel replicatesoperation of a hot engine, and therefore improves combustionperformance. Further, alternate fuels such as ethanol perform poorly incold conditions, and therefore also benefit from pre-heating of fuel.

Various methods of heating fuel at a fuel injector have been attempted.Such methods include the use of a ceramic heater, or a resistivelyheated capillary tube within which the fuel passes. These methodsrequire electric power and therefore leads that extend through pressurebarriers and walls. Seals required between the wires and pressurebarriers are a potential source of fuel leakage and are thereforeundesirable. Further, such heat generating devices must be insulatedfrom other fuel injector components and therefore are difficult toimplement and support within a fuel injector.

Accordingly, it is desirable to design and develop a method of heatingfuel without creating additional fuel leak paths, or insulatingstructures while still providing for the heating and vaporization offuel.

SUMMARY OF THE INVENTION

An example fuel injector assembly includes a first coil that induces acurrent into a second coil that is utilized to inductively andresistively heat fuel flowing through the fuel injector.

The example fuel injector includes a primary coil that receives a firstsignal from a driver to generate a first magnetic field that moves anarmature between an open and closed position. A secondary coil isutilized to heat a component in thermal contact with the fuel flow thatin turn heats fuel before exiting the fuel injector. The heated fuelexiting the fuel injector assembly is heated to a temperature thatsubstantially vaporizes the liquid fuel to achieve a high level ofatomization that in turn improves combustion performance.

The secondary coil generates a second magnetic field generated by acurrent induced by the first coil into the second coil. The inducedcurrent is generated by a second signal that is sent to the first coilin addition to the first signal. The second signal is an alternatingcurrent signal that produces a time varying second magnetic field. Thefrequency of the alternating current that generates the second magneticfield is such that movement of the armature is not induced. Thefrequency of the alternating current results in a time varying andreversing second magnetic field. The time varying second magnetic fieldproduces a flux flow in the surface of the material that alternatesdirection to generate heat.

The example second coil also includes an electrical connection to acomponent in thermal contact with the flow of fuel. The electricalconnection transmits a current into an electrically conductive componentto induce a resistive heating that combined with the inductively heatedcomponent heats and vaporizes fuel within the fuel injector.

Because no hard leads are required to induce the desired second timevarying magnetic field, the second coil can be placed within sealedcompartments and still provide the desired inductive heatingperformance.

These and other features of the present invention can be best understoodfrom the following specification and drawings, the following of which isa brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of an example fuel injector assembly.

FIG. 2A is a sketch representing an example drive signal including analternating current signal interposed on a direct current signal.

FIG. 2B is another sketch representing an example drive signal includingonly the direct current signal.

FIG. 3 is schematic representation of another example fuel injectorassembly.

FIG. 4 is a cross-section of a portion of another example fuel injectorassembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, an example fuel injector 10 includes an annularfuel flow path 24 defined between an armature 26 and a valve body 20.The armature 26 moves within the valve body 20 between an open andclosed position to regulate fuel flow 18 through the annular flow path24. A primary coil 14 receives a first signal from a driver 12 togenerate a first magnetic field that moves the armature 26 between theopen and closed positions. A secondary coil 16 is axially adjacent thefirst coil 14 and is utilized to heat a component in thermal contactwith the fuel flow 18 that in turn heats fuel before exiting the fuelinjector through the outlet 34. The heated fuel exiting the outlet 34 asindicated at 36 is raised to a temperature that substantially vaporizesthe liquid fuel to achieve a high level of atomization that in turnimproves combustion performance.

The component in thermal contact with the fuel flow 18 in this exampleis the valve body 20. The valve body 20 includes electrical connections42 to the secondary coil 16. Current induced in the secondary coil 16 isutilized to resistively heat the valve body 20. The example valve body20 is fabricated from an electrically conductive material that providesa desired resistance to current from the secondary coil 16. The valvebody 20, in turn generates heat in response the amount of current thatis generated and applied.

Further, another component in thermal contact with the fuel flow 18 inthis example is a portion of the armature 26. The armature 26 includesan armature tube 22 disposed within the fuel flow 18. The armature tube22 is fabricated from a magnetically active material that responds to amagnetic field. The secondary coil 16 generates the second magneticfield surrounding and interacting with the armature tube 22. The secondmagnetic field is generated by a current induced by the first coil 14into the second coil 16. The induced current is generated by a secondsignal that is sent to the first coil 14 in addition to the firstsignal. The second signal is an alternating current signal that producesa time varying second magnetic field in the secondary coil 16.

The frequency of the alternating current that generates the secondmagnetic field is such that movement of the armature 26 is not induced.No movement of the armature 26 is induced because the frequency of thealternating current results in a time varying and reversing secondmagnetic field. Heat inside the armature tube 22 is generated byhysteretic and eddy-current loses that are induced by the time varyingsecond magnetic field.

Although the armature tube 22 temperature is elevated, the secondarycoil 16 remains relatively cool and therefore does not require anyspecial thermal insulation accommodations. The amount of heat generatedis determined by the specific resistivity of the material of thearmature tube 22 and the magnitude of the second magnetic field. Thetime varying second magnetic field produces a flux flow in the surfaceof the material that alternates direction to generate heat. The higherthe resistivity of the material the better the generation of heatresponsive to the second magnetic field. The specific material utilizedfor the armature tube 22 is selected to provide the desired generationof thermal energy required to elevate and vaporize fuel within the fuelinjector assembly 10.

Accordingly, two heat generation modes occur simultaneously to providethe desired heat required to elevate the temperature of the fuel flow18. The secondary coil 16 is not electrically connected to any externalpower source. Instead, and current is induced by the primary coil. Thesecondary coil 16 thereby provides heating through inductive heating ofthe armature tube 22 and resistive heating of the valve body 20.

Further, the disclosed example utilizes the armature tube 22 forinductive heating, and the valve body 20 for resistive heating, howeverother components in thermal contact with the fuel flow 18 could also beutilized for each of the different heating modes.

Referring to FIGS. 2A and 2B, a positive lead 38 and a negative lead 40are all that is required to generate the desired first and secondmagnetic fields for the example fuel injector assembly 10. Armaturemovement is powered by the first magnetic field generated within thefirst coil 14 by a direct current 30 as is commonly practiced and known.A second alternating current 32 is imposed on the direct current signal30. The second alternating current 32 is of such a frequency that itdoes not affect the desired open and closing of the armature 26.Further, the second alternating current signal 32 can be turned offduring conditions where heating of the fuel is not desired.

The second alternating current 32 directed to the first coil 14 isutilized to induce the second magnetic field in the second coil 16. Asappreciated, by providing a desired ratio of windings between the firstcoil 14 and the second coil 16 a desired magnitude of the second timevarying magnetic field is provided. Further, the alternating currentsignal 32 interposed onto the first direct current signal 30, generatesthe desired alternating and time varying magnetic field that generatesinductive heating of the armature tube 22 within the fuel flow 18.

Referring to FIG. 3, another example fuel injector assembly 42 includesthe second coil 16 nested within the first coil 14. In the nested coilconfiguration, the first coil 14 and the second coil 16 are coaxiallylocated. The example first coil 14 receives the first direct currentsignal 30 to generate the first magnetic field that moves the armature26. The second alternating current signal 32 interposed on the firstdirect current signal 30 induces the generation of the second magneticfield in the second coil 16. The alternating current in turn generates atime varying and reversing magnetic field that induces heat in thearmature tube 22. The temperature of the armature tube 22 is elevated toa level that causes substantial flash boiling and vaporization of thesurrounding liquid fuel.

Further, the electrical connections 42 between the valve body 20 and thesecondary coil 16 provide a secondary mode of heating the fuel flow 18.The current induced into the secondary coil 16 is directed through thevalve body 20. The electrical resistance of the valve body 20 generatesheat that is also utilized in heating the fuel flow 18.

Referring to FIG. 4, another example fuel injector assembly 44 includesthe second coil 16 disposed within the valve body 20. The valve body 20provides a sealed cavity through which fuel flows. It is desirable tominimize any potential leak paths as is the purpose of inductiveheating. Inducement of the second magnetic field by the first coil 14provides for the location of the second coil 16 within the sealed valvebody 20, and potentially within the fuel flow 18 itself, withoutcreating any additional potential leak paths. The closer proximity ofthe second coil 16 to the armature tube 22 can provide increases inefficiencies resulting in quicker and greater heat generation.

Further, the electrical connections 42 between the valve body 20 and thesecondary coil 16 are within the sealed space and still provideresistive heating. Because the current utilized for resistive heating isinduced by the primary coil 14, and not provided by a hardwireconnection, the resistive heating function and electrical connections 42can be disposed within the sealed chamber and still provide the desireddual heating modes of inductive and resistive heating.

Because no hard leads are required to induce the desired second timevarying magnetic field, it can be placed within sealed compartments andstill provide the desired inductive heating performance. Further,placement of the secondary coil 16 is only limited by the capability ofproducing a second time varying magnetic field of a desired strength toproduce the desired inductive heating to attain the desired level ofvaporized fuel.

Although a preferred embodiment of this invention has been disclosed, aworker of ordinary skill in this art would recognize that certainmodifications would come within the scope of this invention. For thatreason, the following claims should be studied to determine the truescope and content of this invention.

1. A fuel injector assembly comprising: a first coil for generating afirst magnetic field responsive to a first signal; and a second coilinduced with a current by the first coil through electromagneticinduction; and an electrical connection between the second coil and acomponent, wherein the component is in thermal contact with a fuel flowand generates heat through the electrical connection for heating atleast a portion of the fuel flow.
 2. The assembly as recited in claim 1,wherein the second coil generates a second magnetic field responsive toa second signal sent to the first coil and at least one component inthermal contact with the fuel flow is heated responsive to the secondmagnetic field generated by the second coil.
 3. The assembly as recitedin claim 2, wherein the second magnetic field comprises a time varyingmagnetic field that induces hysteretic and eddy current loses within theat least one component.
 4. The assembly as recited in claim 2, whereinthe first signal comprises a direct current and the second signalcomprises an alternating current superimposed onto the first directcurrent signal.
 5. The assembly as recited in claim 2, wherein the firstsignal and the second signal operate independent of each other.
 6. Theassembly as recited in claim 2, including an armature movable responsiveto the first magnetic field for controlling a flow of fuel, wherein aportion of the armature is inductively heated by the second magneticfield.
 7. The assembly as recited in claim 1, including an armaturemovable within a tube that defines an annular fuel flow channel betweenthe armature and the tube.
 8. The assembly as recited in claim 1,wherein the second coil is disposed within the fuel flow.
 9. Theassembly as recited in claim 1, wherein the second coil is nested withinthe first coil.
 10. The assembly as recited in claim 1, wherein thefirst coil is disposed adjacent the second coil.
 11. A method of heatingfuel comprising the steps of: a) generating a first magnetic field in afirst coil responsive to a first signal; b) inducing a current in asecond coil with the first coil through electromagnetic induction; c)electrically connecting at least one component in thermal contact with afuel flow to the second coil; and c) heating the at least one componentwith current induced in the second coil through the electricalconnection.
 12. The method as recited in claim 11, including the step ofinducing a second magnetic field in the second coil responsive to asecond signal transmitted to the first coil.
 13. The method as recitedin claim 12, including the step of heating the same at least onecomponent or another component with the second magnetic field.
 14. Themethod as recited in claim 13, wherein said step b, comprises generatingtime varying magnetic field with the alternating current signal thatinduces hysteretic and eddy current loses within the at least onecomponent to generate heat.
 15. The method as recited in claim 11,wherein the second coil is disposed within the flow of fuel.
 16. Themethod as recited in claim 11, wherein the first signal is a directcurrent signal and the second signal is an alternating currentinterposed onto the direct current signal.
 17. The method as recited inclaim 11, including the step of moving an armature responsive togeneration of the first magnetic field.
 18. The assembly as recited inclaim 1, wherein the second coil is not electrically connected to anyexternal source of current.
 19. The assembly as recited in claim 11,wherein the second coil is not electrically connected to any externalsource of current.